The fluorescent antibody (FA) capabilities of several laboratories have been joined in collaborative research intended to develop FA reagent grade conjugates specific for certain plaque streptococci and filiaments. The prevalence of certain plaque organisms will be determined using both FA methods and conventional cultural methods to estimate the reliability of each method. The purpose of the present study is to provide identification methods and criteria to permit the accurate enumeration of plaque streptococci and certain other plaque organisms considered to be cariogenic. Colored plates have been prepared to portray representative colonial types of each serotype of Strep. mutans, other oral streptococci and selected plaque bacteria. Tabular summaries of the biochemial and physicological characteristics distinguishing each of these plaque bacteria are being prepared.